Research from the last two decades has shown that the initiation, regulation and ending of inflammatory reactions as well as the regulation of growth and differentiation within the mammalian organisms is under tight control by a special group of signal polypeptides generally called cytokines. Cytokines are polypeptides which can be produced by most nucleated cells and which transmit regulatory signals between cells, thus forming a communication network between identical or different cell types of the organism. The cytokines are extremely potent mediators and active at concentrations down to 10.sup.-15 M. Cytokines are also key factors for the development of cellular immune reactions, which in turn form the basis for the clinical manifestations of inflammation due to infection, allergy, trauma, graft vs. host reactions and auto-immune diseases. The allergic and auto-immune diseases are explained by abnormalities in the immune system, especially in the T lymphocyte-mediated immunity, but generally these diseases are of unknown etiology. In vitro studies, animal experiments and clinical experimental studies have shown that cytokines play important pathophysiological roles for the inflammatory reactions related to auto-immune diseases, allergy, ischemia, reperfusion injury, trauma, infections, and are important for the development of cancer, atherosclerosis, pregnancy and fetal development, bone homeostasis. Cytokines may be involved in other immunoinflammatory and proliferative diseases as will be described in further detail in the following.
The said diseases are usually chronic and the treatment is palliative, i.e. most of the drugs prescribed in connection with the said diseases are directed at the allaying of symptoms and usually have no curative effect. Other treatments are so-called substitution therapies which involve life-long supplying to the patient of substances, e.g. hormones, needed due to a reduced/insufficient internal production of said substance. Said treatments are often unsatisfactory, imply unwanted and often serious side-effects, and merely delay rather than prevent the progression of the disease. Thus, improved methods of treatments and improved pharmaceutical compositions are highly needed.
Interleukin-10 (IL-10) is a recently described natural endogenous immunosuppressive cytokine, identified in both the murine and human organism. Murine interleukin 10 (mIL-10) was originally described as a cytokine synthesis inhibitory factor released from TH.sub.2 helper T-cell clones, but it also carries proliferative effects upon various subsets of lymphocytes, including an enhancing effect upon cloning efficacy of CD4-,8.sup.+ murine splenic T cells (4). Human interleukin 10 (hIL-10) has recently been sequenced and revealed to have high homology with mIL-10 at DNA sequence level as well as on amino acid level. Furthermore, swine interleukin 10 has recently been sequenced and revealed to have high homology with human IL-10 at DNA sequence level as well as on amino acid level (88), see also FIG. 2. Also, hIL-10 has high homology with an open reading frame in the Epstein-Barr virus genome, BCRF1, and viral IL-10 does show some activity similar to hIL-10, cf. FIG. 1 (5).
Human IL-10 is produced by activated T cell clones and immortalized B cells, and in addition to its cytokine synthesis inhibitory factor (CSIF) activity, inhibiting the production of several pro-inflammatory cytokines and colony-stimulating factors, it also induces the production of a natural interleukin-1 receptor antagonist protein/peptide (IRAP) by mono-nuclear cells, thereby indirectly inhibiting IL-1 activity. IL-10 also downregulates its own production by monocytes and inhibits the expression of class II MEC expression (12). Further, hIL-10 reduces antigen-specific proliferation of human T cells and CD4.sup.+ T cell clones, when using monocytes as antigen-presenting cells. In vivo experiments in mice indicate that the outcome of Leishmania infection is dependent upon the cytokine profile from responding CD4.sup.+ T lymphocytes (13). In C57BL/6 mice resistant to Leishmania infection, CD4.sup.+ T cells from draining lymph nodes show up-regulation of IFN-.gamma. and IL-2 cytokines, whereas the sensitive BALB/C mice in their draining lymph nodes have CD4.sup.+ responding T cells releasing IL-4 and IL-10, which could be demonstrated to correlate with disease progression (13). Thus, IL-10 may exert potent regulatory effects on immunological responses both in vitro and in viva. Further IL-10 strongly affects chemokine biology since human interleukin 10 is a specific chemotactic factor towards CD8+ T cells, while IL-10 suppresses the ability of CD4+, but not CD8+, T cells to migrate in response to the T cell chemotactic cytokine, IL-8 (14). IL-10 also inhibits the chemotactic effect of other chemokines MCP-1/MCAF and RANTES (75). Since IL-10 is a deactivator of monocyte/macrophage functions and an inhibitor of Th1 activity, drugs with full or partial IL-10-like activity may possess therapeutic effect in diseases characterized by imbalance in cytokine production and/or activities.
It has previously been proposed to prepare pharmaceutical compositions comprising hIL-10 or vIL-10, and the use of hIL-10 or vIL-10 for the manufacture of a pharmaceutical composition for the treatment of various conditions such as septic or toxic shock, rheumatoid arthritis, graft-vs-host disease, tissue rejection, diabetes mellitus, autoimmune disorders, leukaemia and cancer has been disclosed in e.g. WO93/02693 and WO94/04180. Moreover, IL-10 antagonists, e.g. antibodies specifically binding to IL-10, have been disclosed in e.g. EP 405 980 and WO94/06473, and it has been contemplated that such antibodies could be useful in the treatment of HIV infected patients.